1. Field of the Invention
The present invention relates to the technical field of mobile communications and, more particularly, to a method for providing a buffer status report in a mobile communication network.
2. Description of Related Art
In a 3G mobile communication network, a base station of the network side is provided for servicing the user equipments (UEs) in a cell controlled by the base station. Accordingly, the base station needs to understand the working status of the UEs in order to appropriately allocate the resources for a communication without a waste. Uplink traffics existing in a Universal Mobile Telecommunication System High-Speed Uplink Packet Access (UMTS HSUPA) and an Evolved UMTS Terrestrial Radio Access (E-UTRA) applies a network-controlled scheduler mechanism controlled by the network side to complete the requirement cited above. FIG. 1 is a schematic diagram of a base station 12 at the mobile communication network side and a plurality of user equipments 11. For an appropriate resource allocation between the UEs 11, the UE 11 need to provide all uplink scheduling information to the scheduler of the base station 12 of the network side. In a UMTS HSUPA system, such uplink scheduling information contains 18-bit scheduling information (SI) and one happy bit. The SI can provide the amount of system resources needed by the UE 11 and the amount of resources it can actually make use of to the network side, and the happy bit indicates whether the UE 11 can use more resources. As compared to the UMTS systems, an E-UTRA system uses multiple access schemes and system requirements different from the UMTS systems, and thus providing the uplink scheduling information in more detail is required. For example, for a desired agreement between different UEs or different logical channels of a UE, the E-URTA system reports the buffer status of different logical channel groups (LCGs) to the network side, but the UMTS system only reports the buffer status of the highest-priority logical channel and the status occupied by all buffers to the network side.
FIG. 2 is a schematic diagram of a user equipment 11 used to describe a buffer status report (BSR) mechanism, in which the UE 11 has multiple logical channels (LCs) divided into a plurality of logical channel groups (LCGs) 201-204, each LCG 201-204 having no LC or one or more LCs, each LC having a priority. In addition, each LCG 201-204 has a respective buffer 211-214 and buffer status (BS) 221-224, and the buffers 211-214 are independent buffer memory or provided with a single buffer memory. The buffer statuses 221-224 corresponding to the LCGs 201-204 indicate the occupancy of the buffers 211-214 respectively, and the UE 11 accordingly provides a BSR to the base station 12 of the network side. The content of the BSR of the LCGs 201-204 is shown in FIG. 3 in which the BSR contains same length (five bits) and granularity for the BSs 221-224 corresponding to the buffers 211-214. For example, ‘00000’ in the BSR indicates an empty buffer, ‘11111’ indicates a full buffer, and ‘10000’ indicates a half-full buffer.
The BSR mechanism in existing E-UTRA systems uses a process of per LCG reporting in which the essential agreements are shown as follows:
Agreement 1:
A BSR shall be triggered if any of the following events occur:
(1) Uplink data arrives in the buffers of the UE and the data belongs to a logical channel group with higher priority than those for which data already existed in the buffers of the UE;
(2) In the uplink resources allocated to the UE by the base station, the number of padding bits is larger than the size of the [Short/Long] BSR if pending data is filled into a Protocol Data Unit (PDU) to be transmitted;
(3) A serving cell change occurs.
Agreement 2:
In the uplink resources allocated to the UE by the base station, a pending BSR is cancelled in case a PDU to be transmitted can accommodate all pending data but is not sufficient to accommodate the triggered [Short/Long] BSR in addition.
The short BSR provides the buffer status corresponding to a single LCG, with a format shown in FIG. 4 in which a 2-bit LCG identification (ID) field and a 6-bit buffer size field are included. The LCG ID field indicates the corresponding LCG to the reported buffer status, and the buffer size field indicates all pending data amount of all LCs of the corresponding LCG. The long BSR provides the buffer status of all LCGs, with a format shown in FIG. 5 in which there are three bytes having four 6-bit buffer size fields to indicate LCG ID Number 1-4 respectively.
As cited, the UE sends a short BSR with one byte for providing a buffer status report of one LCG or a long BSR with three bytes for providing a buffer status report of four LCGs.
The first agreement defines that an arrival data with higher priority is allowed to trigger a BSR and a scheduling request is triggered to request an available resource allocation when no uplink resource is allocated to send the triggered BSR. However, for the LC with higher priority due to the arrival data, whether the short BSR of the only LCG corresponding to the LC with higher priority is triggered or the long BSR of the LCGs is triggered is not defined.
Supposed that the short BSR of the only LCG corresponding to the LC with higher priority is triggered, it may happen that an empty BSR is triggered. This is because the BSR reports the remaining data amount in the buffer after the pending data in the buffer is filled in the PDU to be transmitted and all data of LCs with higher priority can be completely transmitted upon the current uplink resource allocation in the UE. In this case, triggering the empty BSR causes a resource waste.
In addition, even the BSR of multiple LCGs is triggered due to the data of LCs with high priority, transmitting the empty BSR of an LCG having no remaining data is not required.
Accordingly, the content of uplink scheduling information provided by the UE requires a further optimization for meeting the real requirements and also minimizing the resource waste.
Therefore, it is desirable to provide an improved method to mitigate and/or obviate the aforementioned problems.